Workers discovered a boat under the streets of San Francisco that is thought to be a Gold Rush-era cargo ship, similar to the one pictured here.

Hundreds of ships landed in San Francisco Bay during the Gold Rush years. The boat was discovered two blocks from the current shoreline.

'Pretty Unusual'

"It's actually pretty unusual," said Lynn Cullivan, management assistant at the San Francisco Maritime National Museum. "Normally, you see pieces of larger vessels."

While it is not uncommon to find pieces of ships under the city's streets, it is rare to find a boat as intact as this one, Cullivan added.

After noticing the boat's outline, the workers dug around it by hand to preserve the vessel.

"This in its day was simply a workboat. It's something nobody was interested in. It was so common they didn't even save it; they just buried it," said Cullivan.

The lighter would have been used to carry food and other supplies to land from larger ships that couldn't reach the shallow shore. However, by 1860, the city built piers that allowed big ships to pull up and unload.

If the boat's frame is sturdy enough to be transported, it will be taken to the maritime agency's warehouse east of San Francisco.